After reading some science fiction, I've found myself pondering the ethical ramifications of teleportation, specifically teleportation by use of a "Twinmaker machine." A Twinmaker is a device that scans the person standing within it, sends a signal to a second machine--which creates a copy of the first--and then the original is destroyed. In this case, none of the atoms that make "you" up are present in the second booth, and yet from the perspective of the "you" in the second booth, you're still you. Both copies would be atomically identical, more alike than any twin or clone. It would be, essentially, you.
Or would it? Obviously there are a number of reasons why such a device could not/cannot be created as far as the laws of the universe are concerned (as we currently understand them). First, the ability to measure the position and velocity of every atom within your body (in order to create a duplicate) would violate the Heisenberg Uncertainty Principle.
Secondly, even if we could measure every single atom that makes up a person, the amount of energy necessary to rebuild them on the other end would be crazy high. I'm not hip to the physics, but I think it'd be something on the magnitude of a medium-sized star per person (but don't quote me on that). An enormous amount of energy in any case.
Thirdly, to make sure that the person on the other end would be "you," or at least, have all your thoughts, feelings, and memories, you'd have to figure out a way to A) retrieve that information from the person's brain, B) store that information, C) send that information to the second booth, and C) download that information into the new brain, all of which have a host of problems.
But let's ignore all that. One of the advantages of science fiction is that you don't have to solve those technical issues. You can just say that they have been solved. So imagine that I can step into a booth and press a button. I close my eyes, and when I open them, I step out of the booth somewhere else, like Mars. Everything that makes me "me," the way I react to things, my memories, etc. remain the same. While it's true that the atoms I'd be made of at that point aren't the same ones that made me up a minute ago, it's also true that I no longer possess any of the same atoms I did when I was born.
The way I interpret the Ship of Theseus is that consciousness is selfhood, not the body. If I lose a limb, I am not less myself. If I replace that limb with a prosthetic, I'm not "partly" Colin. I am all-Colin. My body is not what makes me me. However, what happens if I'm not the only Colin around?
Let's go back to the Twinmaker for a moment. Essentially, the Twinmaker teleporter moves people like a combination fax-and-shredder. The piece of paper you fax to someone doesn't really travel to them. The original is still in your machine. They have a copy. The same information, but not the original. Now imagine that all fax machines had shredders built into them. The fax goes through, it prints out on the other end, your version gets destroyed. The information is the important part, right? That's basically how a Twinmaker works.
But if it worked like a regular fax, if I step in the booth on Earth, close my eyes, open them and find myself still on Earth, what happens when I find out there's a me on Mars? I'm the "original," sure, but we've said before that the original doesn't really matter. I know my gut reaction to this issue is to say that the "real" me is the on on Earth, but why? If the process had worked I'd say the real me was the one on Mars. That me has all the same thoughts and feelings as the Earth me does, after all.
And even if the Twinmaker always works perfectly, copying the original before destroying it, what happens if you believe in a soul? When the original is destroyed, do they die? If they do, does their soul go on to the afterlife while a soulless automaton is created? Or does the "new" person get a new soul? Or does the soul transfer over?
I realize teleporation is a pipe dream now, and even if it ever comes to be, it might not work this way, but if it does, I advise you to think carefully before stepping into the booth on your way to the stars.
As for me? I'll see you on Olympus Mons.